ATIC and juvenile idiopathic arthritis: In particular, the efficacy of methotrexate in JIA has been ascribed to the release of anti-inflammatory adenosine, through inhibition of 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase (ATIC) and consequent accumulation of intracellular purine nucleotides (Cronstein et al., 1991; Dervieux et al., 2011; Figure 1).